Pump Size for Sheer Descents

ia_soxfan

In The Industry
Mar 7, 2016
24
Iowa
Hello all,

This spring I plan on adding 6 feet worth of sheer descents to our pool. (2-24" and 2-12"). Using CMP's guidelines that calls for 72 GPM. Between the suction and return side I figure I'll have close to 200' of 2" pipe, 90' of it on the suction side. I would ideally like to have a pump just for these, but am wondering how big of pump to actually use. I've been told a 1-1/2 HP Whisperflo, but am questioning that, as it just barely goes below 30' of TDH on the performance curves. Am I better off going to a less HP pump for 72 GPM?
 

JamesW

TFP Expert
Mar 2, 2011
16,792
As long as you size the pipe correctly, the distance is not an issue. I recommend 2.5" pipe.

A WhisperFlo pump is not a good choice for a fountain.

A water feature pump is designed to power a waterfall at low pressure but higher flow.

Waterfall pumps run at half speed vs regular pumps (1725 rpm vs 3450 rpm).

Alternatively, you can just use the return water from your main pump to feed the falls.
 

ia_soxfan

In The Industry
Mar 7, 2016
24
Iowa
That was my initial line of thinking, to cut in a 3-way on the return side of my Intelliflo filter pump with an actuator to the Easy Touch. Is there any down side to doing this?
 

Silver_2000

Gold Supporter
LifeTime Supporter
Nov 29, 2015
514
Carrollton tx
I have (3) 3 foot sheers and a single VS pump on max rpm doesnt provide enough flow for a consistent look for all 3

Like SWG - I would over size so you can turn down the wattage

Edited to reflect 9 feet of sheers
 

JamesW

TFP Expert
Mar 2, 2011
16,792
The pump should provide enough flow. If not, then the water is probably not all going to the sheer descents.

Using water from the main pump works well in many cases.

The only downside that I can think of is maybe a loss of heat if the water is being heated before going to the sheers.
 

Dodger

Silver Supporter
Sep 17, 2017
641
Silicon Valley, CA
No expert here, but a data point. We have 3 feet (3x12") worth of sheers fed by a dedicated 1HP VS pump. We like the flow amount somewhere between 2000-2400rpm.

We've got 2" pipe that downsizes to 1.5" by the time it tees off behind each of the sheers. Probably 20-25ft of pipe on the intake side, and 50-60 ft out to the sheers.
 
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ia_soxfan

In The Industry
Mar 7, 2016
24
Iowa
The pump should provide enough flow. If not, then the water is probably not all going to the sheer descents.

Using water from the main pump works well in many cases.

The only downside that I can think of is maybe a loss of heat if the water is being heated before going to the sheers.
This is where I thought using a 3 way diverter would work well. Should be able to completely isolate to the descents if needed.

At 72 GPM for all the descents (1 GPM per inch), I didn't see why using the VS to power these would be an issue, but the gentleman that I had been talking to wholeheartedly disagreed. Above all, if it doesn't end up panning out, it would not be a big issue to have to re plumb in a new pump after the fact.
 

JamesW

TFP Expert
Mar 2, 2011
16,792
The Intelliflo should work fine. The three way valve can send all water to the sheers for good effect.

Many builders use WhisperFlo pumps but they're not a good choice.

If you added a pump, where would you add the suction?
 

ia_soxfan

In The Industry
Mar 7, 2016
24
Iowa
Was thinking in wall drains. Have a paver deck so pulling up and replacing wouldn't be too big of an issue.

What at are your reasonings behind not recommending the whisperflo? Just curious.
 

JamesW

TFP Expert
Mar 2, 2011
16,792
Exactly as you suspected, the head curve does not match the application.

The WhisperFlo is designed to be able to generate a lot of pressure.

However, a water feature typically is lower pressure and high flow.

A WhisperFlo will waste a lot of power because it does not meet the application.

Jandy, Pentair and Hayward all have waterfall pumps that are designed for the application.

They provide the correct flow, they are quieter and they use less power.

The operating point for the pump should be in the middle of the pump curve where the graph shows the best efficiency zone.